Up: Multi-period pulsation and amplitude Cephei
Usually, the period analysis of the
Scuti variables
show a frequency near 1-2 cycle per day. This phenomenon is especially obvious in
single-site
observations and is probably due to the extinction and
drift of the photometer. Therefore, we ignored the third frequency of 1.3488 cycle per
day, as confirmation of its existence needs further observations.
The period analysis of DQ Cephei made by
Pena (1983)
for different years showed some
evidences for amplitude variations.
Combining all those results together, we listed the amplitudes of f1 and f2
in different years in Table 3 and plotted them in Fig. 3. We conclude
that:
- 1.
- Amplitude variations of DQ Cephei are observable during a time scale of about
a decade. If such variations are periodic, the period is longer than 46 years.
- 2.
- It seems that the amplitudes of the two pulsation modes vary in opposite
phases, implying energy
conservation.
- 3.
- If the amplitude variations are caused by the beat of two close frequencies,
the split between these
frequencies should be smaller than 0.0008 cycle per day,
which is too small to be explained by a rotating split. If the split is caused by
the overlap of different modes,
DQ Cephei should be a high evolved
Scuti. But this does not agree with the
fact that DQ Cephei is a
Scuti variable near the main sequence.
- 4.
- The calculation made by
Moskalik (1985)
shows that the time scale of amplitude modulation of
Scuti caused by
resonance coupling might reach several years. This does not support the opinion that
the amplitude variation of DQ Cephei can be explained by the resonance coupling. Up
to now, most
Scuti show an amplitude variation with a time scale of about a
decade, which is longer than those obtained with theoretical calculations.
![\begin{figure}
\includegraphics [width=8.8cm]{figure3.ps}\end{figure}](/articles/aas/full/1999/09/ds8175/Timg9.gif) |
Figure 3:
Amplitude variations of two modes |
Table 3:
The amplitude(magnitudes) variations of two frequencies in different
years
 |
Up: Multi-period pulsation and amplitude Cephei
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